can't cum, been faking it almost a year

I know it's awful to do but I feel bad telling him I didn't cum because then he get upset and assumes sex was bad but it's not it's really good just not orgasmic. when he gives me head (which is very rare) I do cum and it's just so relaxing we're engaged now for 5 months and he's the only one I've ever been with so I mean I have Noone to compare him to so it's not like I'm trying to "make up for the past" I just need help on how I should talk to him about it because I don't want to be married and still have to fake it please anyone with advice is greatly appreciated